This invention relates to bedding units and to springs and other components used in such units.
Traditionally, box spring units have been manufactured of many helical coil springs which support an upper deck on a lower frame member. In recent years, some segments of the industry have moved to a more modern construction which utilizes, in lieu of coil springs, nonspiral formed wire springs provided with horizontal torsion bars which have their opposite ends connected to upwardly and downwardly inclined connector bars. Many examples of bedding units with formed wire springs are classified according to the U.S. Classification System in Class 5, Subclasses 247 and 255.
Although bedding units with formed wire springs have performed satisfactorily to the extent that they now occupy a large proportion of the box spring production in this country, the present invention represents significant improvements in this field.
In one respect, the spring disclosed in this specification has particular advantages relating to the manner in which its upper end attaches to and supports a wire grid which forms the mattress supporting deck of the unit. In this regard, the upper portion of the spring provides excellent coverage so that the spring effectively supports a relatively large span and area of the wire grid. Furthermore, the upper portion of the spring has a novel configuration which permits its attachment to many different locations on a wire grid, making it possible to change distances between adjacent springs without changing the spacing between the grid wires.
By utilizing the principles of this invention, it is possible to reduce the number of springs and the total amount of spring wire required to provide effective support of a wire grid of any given size.
From a performance standpoint, the bedding units disclosed in this specification are believed to have a lower susceptibility to damage when they are subjected to extreme forces and impacts. The springs have two vertically collapsible columns which are located reasonably close to each other to avoid overloading of one column and to ensure that shock forces imposed on the springs will be shared by both columns. The lower portion or base of the spring is preferably constructed to provide a stable platform which requires a minimum number of staples or other fasteners to connect it to the frame of the bedding unit.
The disclosed apparatus is also desirable due to the particular arrangements whereby the springs are limited deflection springs, i.e. springs which are deflectable only a predetermined distance. Utilizing the novel configurations of the invention, the deflection of a spring stops when a torsion bar in its midportion is contacted by a grid wire or by the upper attachment portion of the spring body.
The invention also involves a novel corner spring which is effective due to its utilization of a torsion bar principle. The corner spring preferably has limited deflection characteristics.
In another respect, the invention involves improvements based on the utilization of simple and inexpensive pieces which are attached to the wire grid to limit its downward movement, preferably at the corners of the unit where the pieces also serve to prevent inward sagging of the filling material of the unit.
Furthermore, the invention includes a novel arrangement for clipping the spring to a wire grid of a bedding unit, wherein a yieldable plastic material is coated on the interior of an attachment clip to avoid the necessity of coating the springs and/or the grid wires which are clipped together.
Finally, the invention is directed to a construction which permits the utilization of a relatively lightweight wire grid, and a minimum amount of spring wire, staples and attachment clips. Other attributes of the invention may be seen from the accompanying description of a few embodiments of the invention.